This invention relates to a method for machining by means of thermal shock, which method is suitable particularly for machining work blanks of a material which is not easily machined.
For use in melt cutting, grooving, drilling and otherwise machining work blanks, various heat sources such as, for example, welding flame (acetylene), arc (electric), plasma arc, electron beam and laser are properly selected in conformity with the fusibility of particular materials of such work blanks subjected to machining.
When a metal blank of cast iron is melt-cut by plasma arc, for example, the desired melt-cutting is effected by causing the plasma arc to pass along a precribed cutting line in the work blank. In this case, the removal of the product of fusion by plasma arc is accomplished by use of a forced current of a cutting gas directed toward the part of the work blank being machined.
A method which effects the removal of the fused material by directing a jet of water toward the points of machining in the work blank has also been suggested (U.S. Pat. No. 3,967,090).
When the work blank happens to be a piece with low malleability such as a thick plate of cast iron which permits no flash cutting or drilling, however, effective expulsion of the fused material cannot be obtained by injecting a cutting gas or jet of water. Thus the machining operation inevitably consumes a hugh volume of energy and much time.
An object of this invention is to provide a method for economically and rapidly machining work blanks made of materials having particularly low malleability by means of thermal shock.